Flask (IMAGE) University of Washington Caption The Lake Washington mud samples were mixed with food labeled with a heavy isotope of carbon, allowing researchers to look at DNA only from organisms that ate the labeled food. Credit Ekaterina Latypova Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.